Respiratory failure ((NRF) is a common cause of death in newborn infants. Life support with extracorporeal membrane oxygenation (ECMO) is a unique tool to study the pathophysiology of this disorder. Our initial clinical application of ECMO to moribund infants with critical respiratory failure resulted in a 46% survival. Thus use of ECMO obviates the need for high FiO2 and ventilator pressures which are suspected of contributing to mortality and morbidity (bronchopulmonary dysplasia) in NRF. This proposal describes a combined laboratory and clinical study using ECMO to investigate the hemodynamic, pulmonary, and hematologic changes that occur with severe respiratory failure in the newborn. It includes evaluation of a method for measuring NRF and predicting mortality risk. This section of the study is essential to characterize the course of NRF with variables in management and to define indications for specific management techniques such as ECMO. The effects of ECMO management will be evaluated by comparing ECMO-treated infants (low FiO2 and ventilator pressure) to infants treated with optimal current therapy (high FiO2 and ventilator pressure when necessary). From the results of the laboratory and clinical studies we propose to design a controlled-randomized study of ECMO in the newborn for later implementation.